High-Reynolds-number flow past many blades in extreme ground effect

High speed flow past many aligned, sequential aerofoils is considered, particularly concentrating on the regime where the gaps between the blades and the ground are small, using theory and computation. The flows considered are two-dimensional and laminar with a focus on the physical flow mechanisms for high-Reynolds-number flows. In particular: viscous–inviscid interaction that determines much of the flow between each blade and the ground, strong upstream influence, abrupt pressure jumps at each leading edge, and significant downstream influence and slip-streaming effects. Calculations are presented for the pressures and shear stresses, the lift, the frictional drag and the velocity profiles. The asymptotic limits of small and large clearance are considered. Numerical results suggest a near periodic many-blade limit emerges once enough blades are passed.